RESEARCHES IN HELMINTHOLOGV AND PARASITOLOGY. 175 



Tenth segment, 3 setae and 18 hooks, but on one side the latter 

 were all imperfect, mostly with the comb undeveloped. 



Eleventh segment, 2 setae and 14 hooks each side. 



In the last specimen the rows of 24 hooks in the ninth segment 

 measured 0.08 mm. wide ; the rows of 18 hooks of the tenth seg- 

 ment 0.072 mm. wide, and the rows of 14 hooks of the last segment 

 0.06 mm. wide. The height of the rows corresponding with the 

 length of the hooks was 0.025 mm. 



The intestinal canal of Manayunkia is of extreme simplicity, con- 

 sisting of a median tube alternately dilated within the segments and 

 contracted in the intervals of the latter, without any other conspicu- 

 ous division into more distinct portions. The widest expansions are 

 within the fourth to the seventh segment, inclusive, but are also 

 variable in these. Afterwards the intestine becomes narrower to 

 the anus, which opens ventrally in the last segment. The mouth is 

 funnel-like, capacious, and without armature of any kind. Along 

 the intermediate two-thirds of the canal the walls are of a yellowish 

 brown hue. Within the intestine in the seventh segment, and within 

 the terminal portion, active ciliary motion was observed. The in- 

 testine, as usual in other annelides, is connected by thin diaphragms 

 to the wall of the body cavity in the intervals of the segments. The 

 intervals are occupied with liquid with multitudes of floating cor- 

 puscles. 



The ovaries, with ova iu different stages, occupy the fourth to the 

 sixth segment, inclusive. Within the lower part of the head, ex- 

 tending thence into the third segment on each side, there is a large 

 elliptical organ, which I have suspected to be the testicle, though I 

 did not examine its structure. 



I was greatly puzzled in the attempt to ascertain the arrangement 

 of the vascular system of Manayunkia, and am in doubt as to the 

 following explanation I give of it : The blood is of a bright green 

 color, and in many positions serves clearly to define the course of 

 the larger vessels. As represented in figure i , the chief blood vessels 

 appear to be a large one on each side of the intestinal canal, closely 

 following the course of this, so as to seem to form a green coat to it. 

 In each segment of the body the vessel gives off a pair of lateral 

 branches, apparently uniting in a loop. In the head the two main 

 vessels leave the sides of the intestine, and, after forming a close 

 flexure or a sinus at the base of each lophophore, proceed onward 

 through the interior of the larger pair of tentacles. In viewing the 

 worm in any direction, the two main vessels so constantly appeared 

 at the sides of the intestine that I at first took them for the walls of 



